[llvm-dev] Building llvm with clang and lld on arm and the llvm arm backend relocation on position independent code

Alessandro Pistocchi via llvm-dev llvm-dev at lists.llvm.org
Thu Jun 29 14:09:34 PDT 2017 

Hi, I tried patching and rebuilding and now I get this error. Did I miss anything?

/home/yawmoo/Desktop/clfs/sources/llvm/tools/lld/ELF/InputFiles.cpp:82:23: error: 
      no matching constructor for initialization of 'llvm::DWARFDebugLine'
  DwarfLine.reset(new DWARFDebugLine(&Dwarf.getLineSection().Relocs));
                      ^              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/yawmoo/Desktop/clfs/sources/llvm/include/llvm/DebugInfo/DWARF/DWARFDebugLine.h:27:7: note: 
      candidate constructor (the implicit move constructor) not viable: no known
      conversion from 'const RelocAddrMap *' (aka 'const DenseMap<unsigned long,
      llvm::RelocAddrEntry> *') to 'llvm::DWARFDebugLine' for 1st argument
class DWARFDebugLine {
      ^
/home/yawmoo/Desktop/clfs/sources/llvm/include/llvm/DebugInfo/DWARF/DWARFDebugLine.h:27:7: note: 
      candidate constructor (the implicit copy constructor) not viable: no known
      conversion from 'const RelocAddrMap *' (aka 'const DenseMap<unsigned long,
      llvm::RelocAddrEntry> *') to 'const llvm::DWARFDebugLine' for 1st argument
/home/yawmoo/Desktop/clfs/sources/llvm/include/llvm/DebugInfo/DWARF/DWARFDebugLine.h:27:7: note: 
      candidate constructor (the implicit default constructor) not viable:
      requires 0 arguments, but 1 was provided
/home/yawmoo/Desktop/clfs/sources/llvm/tools/lld/ELF/InputFiles.cpp:89:34: error: 
      no viable conversion from 'llvm::DataExtractor' to 'const
      llvm::DWARFDataExtractor'
  DwarfLine->getOrParseLineTable(LineData, 0);
                                 ^~~~~~~~
/home/yawmoo/Desktop/clfs/sources/llvm/include/llvm/DebugInfo/DWARF/DWARFDataExtractor.h:20:7: note: 
      candidate constructor (the implicit copy constructor) not viable: cannot
      bind base class object of type 'llvm::DataExtractor' to derived class
      reference 'const llvm::DWARFDataExtractor &' for 1st argument
class DWARFDataExtractor : public DataExtractor {
      ^
/home/yawmoo/Desktop/clfs/sources/llvm/include/llvm/DebugInfo/DWARF/DWARFDataExtractor.h:20:7: note: 
      candidate constructor (the implicit move constructor) not viable: cannot
      bind base class object of type 'llvm::DataExtractor' to derived class
      reference 'llvm::DWARFDataExtractor &&' for 1st argument
/home/yawmoo/Desktop/clfs/sources/llvm/include/llvm/DebugInfo/DWARF/DWARFDebugLine.h:237:66: note: 
      passing argument to parameter 'DebugLineData' here
  const LineTable *getOrParseLineTable(const DWARFDataExtractor &DebugLineData,
                                                                 ^
2 errors generated.
tools/lld/ELF/CMakeFiles/lldELF.dir/build.make:494: recipe for target 'tools/lld/ELF/CMakeFiles/lldELF.dir/InputFiles.cpp.o' failed
make[2]: *** [tools/lld/ELF/CMakeFiles/lldELF.dir/InputFiles.cpp.o] Error 1
CMakeFiles/Makefile2:49925: recipe for target 'tools/lld/ELF/CMakeFiles/lldELF.dir/all' failed
make[1]: *** [tools/lld/ELF/CMakeFiles/lldELF.dir/all] Error 2
Makefile:149: recipe for target 'all' failed
make: *** [all] Error 2


> On 28 Jun 2017, at 19:04, Shoaib Meenai <smeenai at fb.com> wrote:
> 
> The bottom of the bug has the revision numbers (e.g. D34035). That one
> corresponds to e.g. https://reviews.llvm.org/D34035
> 
> There's also https://reviews.llvm.org/D34634 which contains all of Peter's
> patches, but it's not going to rebase cleanly once the individual patches
> start going in.
> 
> On 6/28/17, 10:56 AM, "Alessandro Pistocchi" <apukfreelance at gmail.com> wrote:
> 
>    Sorry for the noob question: where do I get the patches?
> 
>    I can see the bug but not a link to the patches ( I don't have a login if that is the issue )
> 
>    Sent from my iPhone
> 
>> On 28 Jun 2017, at 19:36, Shoaib Meenai <smeenai at fb.com> wrote:
>> 
>> I've successfully used Peter's patches to get past those relocation errors.
>> 
>> On 6/28/17, 9:36 AM, "llvm-dev on behalf of Peter Smith via llvm-dev" <llvm-dev-bounces at lists.llvm.org on behalf of llvm-dev at lists.llvm.org> wrote:
>> 
>>   Yes it should cover the following relocations:
>>   R_ARM_CALL (ARM BL/BLX)
>>   R_ARM_JUMP24 (ARM B)
>>   R_ARM_THM_CALL (Thumb BL/BLX)
>>   R_ARM_THM_JUMP19 (Thumb conditional B<cc>.w)
>>   R_ARM_THM_JMP24 (Thumb unconditional B.w)
>> 
>>   Peter
>> 
>> 
>>>   On 28 June 2017 at 17:31, Alessandro Pistocchi <apukfreelance at gmail.com> wrote:
>>> Oh, so it looks like I hit a bit of a wall there :-) I’ll take a look thanks.
>>> 
>>> That bug talks about R_ARM_THM_CALL which I assume are thumb related.
>>> 
>>> Will your implementation fix also R_ARM_CALL errors?
>>> 
>>>> On 28 Jun 2017, at 17:15, Peter Smith <peter.smith at linaro.org> wrote:
>>>> 
>>>> Hello Alessandro,
>>>> 
>>>> The LLD ARM port doesn't currently support range extension thunks,
>>>> these are needed to extend the range of ARM branch relocations when
>>>> the size of the executable instructions exceeds the maximum branch
>>>> range.
>>>> 
>>>> I have an implementation in review but it is a fairly large change so
>>>> it may take some time to get through the review process, I've raised
>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.llvm.org_show-5Fbug.cgi-3Fid-3D33612&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=MoG8NHuM6pLu1J1B-yHnV-uqDvXgdp72ydIhDlNyQ9Q&s=RpqKAJtCInfokC4ejkvv1e1hbMx22g7c6-v8JNuzOrY&e=  that has a link to the
>>>> Phab reviews. If you are willing to build your own lld with additional
>>>> changes, you might be able to test out those patches.
>>>> 
>>>> Good luck
>>>> 
>>>> Peter
>>>> 
>>>>> On 28 June 2017 at 17:09, Alessandro Pistocchi <apukfreelance at gmail.com> wrote:
>>>>> 
>>>>>> On 27 Jun 2017, at 13:25, Peter Smith <peter.smith at linaro.org> wrote:
>>>>>> 
>>>>>> Hello Alessandro,
>>>>>> 
>>>>>> Despite the statement in the HowToCrossCompileLLVM guide "If you’re
>>>>>> using Clang as the cross-compiler, there is a problem in the LLVM ARM
>>>>>> back-end that is producing absolute relocations on
>>>>>> position-independent code (R_ARM_THM_MOVW_ABS_NC), so for now, you
>>>>>> should disable PIC:" I can't find an existing upstream PR or any
>>>>>> record that this has been fixed. If the ARM backend is still producing
>>>>>> an R_ARM_THM_MOVW_ABS_NC relocation when -fpic is given as an option
>>>>>> then it would be great to get a small reproducible example in a new
>>>>>> PR, or if there is one already to update it.
>>>>>> 
>>>>>> The last time I ran into this error when trying to cross compile was
>>>>>> that a dependency not compiled by clang (libtinfo.a) library contained
>>>>>> an R_ARM_THM_MOVW_ABS_NC relocation. I don't think that this is the
>>>>>> fault of clang/llvm though, I think it was my fault in installing a
>>>>>> non pic compiled version of libtinfo.a (I'm still trying to learn how
>>>>>> Ubuntu multilibs work).
>>>>>> 
>>>>>> Would it be possible for you to share the details of which objects
>>>>>> contain the R_ARM_THM_MOVW_ABS_NC relocations when compiled -fpic?
>>>>> 
>>>>> Hi, the errors I get do not seen to mention R_ARM_THM_MOVW_ABS_NC.
>>>>> 
>>>>> The errors are “relocation R_ARM_CALL out of range”.
>>>>> 
>>>>> Today I recompiled everything from scratch with -fPIC to make sure I had no library compiled without it and I still get the same errors.
>>>>> 
>>>>> Sorry, I could not find any trivial code that has the same issue yet.
>>>>> 
>>>>> Following is the output of the compilation process:
>>>>> 
>>>>> yawmoo at yawmoo-MRNM3AP:~/Desktop/clfs/sources/llvm-build-native-with-lld$ cmake --build .
>>>>> [  0%] Built target LLVMDemangle
>>>>> [  3%] Built target LLVMSupport
>>>>> [  3%] Built target LLVMTableGen
>>>>> [  4%] Built target obj.llvm-tblgen
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>>>>> [ 85%] Linking CXX executable ../../../../bin/clang
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCAliasAnalysis.cpp:(function llvm::Pass* llvm::callDefaultCtor<llvm::objcarc::ObjCARCAAWrapperPass>()): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCAliasAnalysis.cpp:(function llvm::Pass* llvm::callDefaultCtor<llvm::objcarc::ObjCARCAAWrapperPass>()): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/tools/clang/lib/StaticAnalyzer/Core/CallEvent.cpp:(function clang::ento::CXXDestructorCall* clang::ento::CallEventManager::create<clang::ento::CXXDestructorCall, clang::CXXDestructorDecl const*, clang::Stmt const*, clang::ento::MemRegion const*, bool>(clang::CXXDestructorDecl const*, clang::Stmt const*, clang::ento::MemRegion const*, bool, llvm::IntrusiveRefCntPtr<clang::ento::ProgramState const>, clang::LocationContext const*)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCAliasAnalysis.cpp:(function llvm::Pass* llvm::callDefaultCtor<llvm::objcarc::ObjCARCAAWrapperPass>()): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCAliasAnalysis.cpp:(function llvm::Pass* llvm::callDefaultCtor<llvm::objcarc::ObjCARCAAWrapperPass>()): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCAliasAnalysis.cpp:(function llvm::Pass* llvm::callDefaultCtor<llvm::objcarc::ObjCARCAAWrapperPass>()): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCAnalysisUtils.cpp:(function llvm::cl::opt<bool, true, llvm::cl::parser<bool> >::opt<char [21], llvm::cl::desc, llvm::cl::LocationClass<bool>, llvm::cl::initializer<bool> >(char const (&) [21], llvm::cl::desc const&, llvm::cl::LocationClass<bool> const&, llvm::cl::initializer<bool> const&)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCAnalysisUtils.cpp:(function llvm::cl::opt<bool, true, llvm::cl::parser<bool> >::opt<char [21], llvm::cl::desc, llvm::cl::LocationClass<bool>, llvm::cl::initializer<bool> >(char const (&) [21], llvm::cl::desc const&, llvm::cl::LocationClass<bool> const&, llvm::cl::initializer<bool> const&)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCAnalysisUtils.cpp:(function llvm::cl::opt<bool, true, llvm::cl::parser<bool> >::opt<char [21], llvm::cl::desc, llvm::cl::LocationClass<bool>, llvm::cl::initializer<bool> >(char const (&) [21], llvm::cl::desc const&, llvm::cl::LocationClass<bool> const&, llvm::cl::initializer<bool> const&)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCAnalysisUtils.cpp:(function _GLOBAL__sub_I_ObjCARCAnalysisUtils.cpp): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCInstKind.cpp:(function llvm::objcarc::operator<<(llvm::raw_ostream&, llvm::objcarc::ARCInstKind)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCInstKind.cpp:(function llvm::objcarc::operator<<(llvm::raw_ostream&, llvm::objcarc::ARCInstKind)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCInstKind.cpp:(function llvm::objcarc::GetFunctionClass(llvm::Function const*)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/tools/clang/lib/StaticAnalyzer/Core/CallEvent.cpp:(function clang::ento::CXXDestructorCall* clang::ento::CallEventManager::create<clang::ento::CXXDestructorCall, clang::CXXDestructorDecl const*, clang::Stmt const*, clang::ento::MemRegion const*, bool>(clang::CXXDestructorDecl const*, clang::Stmt const*, clang::ento::MemRegion const*, bool, llvm::IntrusiveRefCntPtr<clang::ento::ProgramState const>, clang::LocationContext const*)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCInstKind.cpp:(function llvm::objcarc::GetFunctionClass(llvm::Function const*)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCInstKind.cpp:(function llvm::objcarc::GetFunctionClass(llvm::Function const*)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCInstKind.cpp:(function llvm::objcarc::GetFunctionClass(llvm::Function const*)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCInstKind.cpp:(function llvm::objcarc::GetFunctionClass(llvm::Function const*)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCInstKind.cpp:(function llvm::objcarc::GetFunctionClass(llvm::Function const*)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: /home/yawmoo/Desktop/clfs/sources/llvm/lib/Analysis/ObjCARCInstKind.cpp:(function llvm::objcarc::GetFunctionClass(llvm::Function const*)): relocation R_ARM_CALL out of range
>>>>> /home/yawmoo/Desktop/clfs/llvm-cross-tools-lld/bin/ld.lld: error: too many errors emitted, stopping now (use -error-limit=0 to see all errors)
>>>>> clang-5.0: error: linker command failed with exit code 1 (use -v to see invocation)
>>>>> tools/clang/tools/driver/CMakeFiles/clang.dir/build.make:227: recipe for target 'bin/clang-5.0' failed
>>>>> make[2]: *** [bin/clang-5.0] Error 1
>>>>> CMakeFiles/Makefile2:11670: recipe for target 'tools/clang/tools/driver/CMakeFiles/clang.dir/all' failed
>>>>> make[1]: *** [tools/clang/tools/driver/CMakeFiles/clang.dir/all] Error 2
>>>>> Makefile:149: recipe for target 'all' failed
>>>>> make: *** [all] Error 2
>>>>> yawmoo at yawmoo-MRNM3AP:~/Desktop/clfs/sources/llvm-build-native-with-lld$
>>>>> 
>>>>> 
>>>>>> 
>>>>>> Peter
>>>>>> 
>>>>>> On 27 June 2017 at 11:47, Alessandro Pistocchi via llvm-dev
>>>>>> <llvm-dev at lists.llvm.org> wrote:
>>>>>>> 
>>>>>>> On 26 Jun 2017, at 16:25, Rui Ueyama <ruiu at google.com> wrote:
>>>>>>> 
>>>>>>> On Sun, Jun 25, 2017 at 6:40 AM, Alessandro Pistocchi via llvm-dev
>>>>>>> <llvm-dev at lists.llvm.org> wrote:
>>>>>>>> 
>>>>>>>> Hi,
>>>>>>>> 
>>>>>>>> I am trying to build a completely GNU free linux toolchain for the
>>>>>>>> raspberry pi.
>>>>>>>> 
>>>>>>>> I successfully managed to compile llvm and clang for armv7 hard float (
>>>>>>>> both as a cross compiler and as a native compiler ) together with the
>>>>>>>> following:
>>>>>>>> 
>>>>>>>> Llvm with clang and lld
>>>>>>>> Clang builtins
>>>>>>>> Musl libc
>>>>>>>> libc++, libc++abi, libunwind
>>>>>>>> 
>>>>>>>> All works well with the only thing to notice being the need to use -fPIC
>>>>>>>> in order to access some library functions when my own c/c++ programs access
>>>>>>>> those functions.
>>>>>>>> 
>>>>>>>> The fact seems to be that musl libc exports some symbols as protected (
>>>>>>>> probably correctly ) and lld ( probably correctly ) says it cannot preempt
>>>>>>>> those symbols.
>>>>>>>> For this reason I seem to have to use -fPIC in the C and CXX flags but
>>>>>>>> everything seems to work ok.
>>>>>>> 
>>>>>>> 
>>>>>>> Is this the same problem mentioned in
>>>>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.llvm.org_show-5Fbug.cgi-3Fid-3D32425-3F&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=MoG8NHuM6pLu1J1B-yHnV-uqDvXgdp72ydIhDlNyQ9Q&s=NukMRJ9yTsw5j3ENYmb5P6xnVjqZDGr_RtEBf88y-aI&e= 
>>>>>>> 
>>>>>>> 
>>>>>>> My aim is to build llvm+clang+lld using llvm+clang+lld on arm ( using musl,
>>>>>>> libc++, libc++abi, libunwind and the clang builtins, no gcc runtime at all
>>>>>>> ).
>>>>>>> 
>>>>>>> I think the fact that lld cannot preempt some symbols without using -fPIC is
>>>>>>> similar to the problem mentioned in
>>>>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.llvm.org_show-5Fbug.cgi-3Fid-3D32425&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=MoG8NHuM6pLu1J1B-yHnV-uqDvXgdp72ydIhDlNyQ9Q&s=9sykAqiCyyRAxvbFBkT7xc41tFV4gbqVNlLPtuZwgEo&e=  .
>>>>>>> 
>>>>>>> However I am not particularly bothered at this stage about having to use
>>>>>>> -fPIC. That would be fine.
>>>>>>> 
>>>>>>> What I am struggling with is that having to use -fPIC is in conflict with
>>>>>>> the arm backend issue that creates bad relocations when building clang with
>>>>>>> -fPIC as mentioned in https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_docs_HowToCrossCompileLLVM.html&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=MoG8NHuM6pLu1J1B-yHnV-uqDvXgdp72ydIhDlNyQ9Q&s=ZDjTpKgbVvk-6KPfK36_iXsQkmN0tZo-GFLmojAfWdI&e=  and so
>>>>>>> the build with -fPIC fails when building the clang binary.
>>>>>>> 
>>>>>>> Regarding https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.llvm.org_show-5Fbug.cgi-3Fid-3D32425&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=MoG8NHuM6pLu1J1B-yHnV-uqDvXgdp72ydIhDlNyQ9Q&s=9sykAqiCyyRAxvbFBkT7xc41tFV4gbqVNlLPtuZwgEo&e=  , please notice that
>>>>>>> contrary to what is reported there I definitely can build and execute a C
>>>>>>> hello world program without having to use -fPIC.
>>>>>>> 
>>>>>>> It is only some symbols from musl that cannot be preempted by lld, not all
>>>>>>> of them.
>>>>>>> 
>>>>>>> Unfortunately, when building llvm+clang+lld quite a few of those symbols are
>>>>>>> explicitly looked for by cmake and not found unless I use -fPIC.
>>>>>>> 
>>>>>>> If I go ahead and build without using -fPIC then the build fails because it
>>>>>>> cannot preempt those symbols.
>>>>>>> 
>>>>>>> It looks like a paradox to me and I think the solution would be to fix the
>>>>>>> fact that the arm backend does not like -fPIC as mentioned in
>>>>>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_docs_HowToCrossCompileLLVM.html&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=MoG8NHuM6pLu1J1B-yHnV-uqDvXgdp72ydIhDlNyQ9Q&s=ZDjTpKgbVvk-6KPfK36_iXsQkmN0tZo-GFLmojAfWdI&e=  . While it is probably
>>>>>>> correct that lld says it cannot preempt protected symbols, the arm backend
>>>>>>> issue is a known issue.
>>>>>>> 
>>>>>>> 
>>>>>>>> 
>>>>>>>> Then I tried to use this compiler ( both the cross compiler and the native
>>>>>>>> compiler ) to compile llvm + clang + lld ( I want to have the toolchain
>>>>>>>> built with itself, again without any GNU software involved ) but when
>>>>>>>> building the clang executable I ran into the arm relocation problems
>>>>>>>> mentioned here in the “Hacks” section when using -fPIC:
>>>>>>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_docs_HowToCrossCompileLLVM.html&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=MoG8NHuM6pLu1J1B-yHnV-uqDvXgdp72ydIhDlNyQ9Q&s=ZDjTpKgbVvk-6KPfK36_iXsQkmN0tZo-GFLmojAfWdI&e=  .
>>>>>>>> On the other hand, I seem to need -fPIC otherwise cmake fails to find some
>>>>>>>> libc functions such as futimes/futimens and many others. If I use -fPIC for
>>>>>>>> CFLAGS but not for CXXFLAGS then cmake finds those symbols but then
>>>>>>>> obviously fails at a later stage with lld unable to preempt those symbols.
>>>>>>>> 
>>>>>>>> This seems to be a conflict I cannot solve without someone within the llvm
>>>>>>>> team fixing the arm relocation problem. Is there any estimate of when this
>>>>>>>> could happen? I am happy to spend the time testing any solutions by building
>>>>>>>> my own toolchain until it succeeds. Or is there any other solution?
>>>>>>>> 
>>>>>>>> Thank you,
>>>>>>>> Alex
>>>>>>>> 
>>>>>>>> 
>>>>>>>> _______________________________________________
>>>>>>>> LLVM Developers mailing list
>>>>>>>> llvm-dev at lists.llvm.org
>>>>>>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.llvm.org_cgi-2Dbin_mailman_listinfo_llvm-2Ddev&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=MoG8NHuM6pLu1J1B-yHnV-uqDvXgdp72ydIhDlNyQ9Q&s=elMtK81LIlpU0bdvd9Zwk2UtgI9He36ddrHDrVDKt94&e= 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> _______________________________________________
>>>>>>> LLVM Developers mailing list
>>>>>>> llvm-dev at lists.llvm.org
>>>>>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.llvm.org_cgi-2Dbin_mailman_listinfo_llvm-2Ddev&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=MoG8NHuM6pLu1J1B-yHnV-uqDvXgdp72ydIhDlNyQ9Q&s=elMtK81LIlpU0bdvd9Zwk2UtgI9He36ddrHDrVDKt94&e= 
>>>>>>> 
>>>>> 
>>> 
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